Mint is one of the oldest of herbs. It was used by the ancient Assyrians, and was common to the ancient Greeks and Romans, who recognized its pain-killing properties. The mint-after-a meal custom in fact dates back to ancient Rome, and Pliny, the first-century Roman historian and scientist, included mint in his Natural History in 77 A.D. Mint was not used formally in medicine until the mid-18th century, but mint tea has been a favorite cure for indigestion since Biblical times. Modern peppermint is actually a hybrid of water mint and spearmint, and has stronger medicinal properties than either of the two originating plants.
Menthol and methyl salicylate are the main active ingredients of peppermint. Internally, they have anti-spasmodic actions, with calming effects on the muscles of the stomach, intestinal tract, and uterus. They also have powerful analgesic (pain-killing) properties, which are mediated, in part, through activation of kappa-opioid receptors, which help block pain signal transmission.
As a high volatile oil peppermint tea, extract, or as enteric-coated peppermint oil capsules, peppermint is extremely useful for indigestion and GI cramps. It is anti-bacterial, increases gastric juices, and relieves gas, nausea, vomiting, and morning sickness. Peppermint also contains essential oils that stimulate the gallbladder to secrete its store of bile, which the body uses to digest fats. This makes peppermint a wonderful digestive aid for heavy meals. It also improves the function of the muscles that line the stomach and intestines, relieves diarrhea, and has a calming, numbing effect on the entire GI tract.
I find peppermint to be the strongest anti-spasmodic and pain reliever of all the herbs, and when an attack flares I really appreciate its noticeable whole-body mild anesthetic effect as well. On a daily basis I find it more effective (and certainly more enjoyable) than prescription anti-spasmodic drugs, particularly when it's brewed as a very strong tea.
In fact, peppermint is such a powerful muscle relaxant that it can trigger GERD (Gastroesophageal Reflux Disease) or heartburn in people who are susceptible. If you are prone to these upper GI problems, avoid mint and stick to the other IBS herbs and spices such as high volatile oil fennel or ginger.
One of the easiest and most effective way to use peppermint for IBS is to brew it (fresh or dried) with boiling water into hot tea (do not actually boil the herb in water as this can destroy its volatile oils, and thus its effectiveness). Peppermint, however, is available in several other beneficial forms as well.
Enteric-coated peppermint oil capsules can be taken before meals to help prevent IBS symptoms. These capsules have been proven highly effective (and safe) in several clinical trials, including studies that focused specifically on children with IBS. These capsules are specially coated so they don't dissolve in the stomach (which could trigger heartburn); instead, they dissolve in the intestines, where they act as a smooth muscle relaxant and pain killer.
Even Altoids, the "curiously strong" peppermint candies, can have a soothing effect on the gut, as can other foods, drinks, or candies that contain pure peppermint oil. I've been known to pop Altoids before or after meals as a safety precaution, either chewing them or just swallowing a couple whole. Fresh breath and no IBS - what more could anyone want?
It's much less expensive to buy dried peppermint in bulk and brew it with tea strainers than to purchase as tea bags (though the effectiveness is comparable and tea bags are more conveniently portable). Peppermint tea (which, like all of the herbal teas for IBS, is naturally caffeine-free as it does not contain any actual tea leaves) can be sweetened with a little honey or plain sugar if you wish but I also think it's delicious plain. It can be chilled into iced tea also, but remember that ice-cold beverages on an empty stomach can trigger GI spasms, whereas the heat in hot teas is in and of itself a muscle relaxant. To make peppermint tea, simply brew 1-2 tablespoons dried (or 3-4 tablespoons fresh) mint leaves per eight ounce cup of fresh boiling water. The stronger the tea, the more pronounced its beneficial effects on your digestion, so don't be afraid to make a dark brew!